I am very happy with my HPA kit. It uses 355 mm Front 6 piston and 335mm Rear 4 piston. The rear design deletes the screw type e-brake calliper and uses a drum style that goes inside the hub of the rear disc. Works great and allows the rear calliper to get the 4 piston design rather than just one like the VW design.

We got these so that we can stop our 2,000 lbs trailer if the trailer brakes should not work
when needed.

We had to do the VR6 spindle swap as well. It seems that VW never thought these TDI cars could go fast enough to really need bigger brakes so we got the little parts (probably from a MK2 or whatever they had lying around)!

Google "HPA Motorsports" if you are interested. They have sales on these kits from time to time.

1. I got set of brand new wheel bearings for TDI and wondering if I could use them on VR6 spindle.
2. Multi piston callipers usually go on 30mm + rotors in terms of thickness. Can a multi-piston calliper be installed on 22mm rotor? (roughly 1cm thinner)

Firstly, VR6 rears are the same as TDI rears. The bigger ones are from the GLI or R32. Having said that, the rears are easier to upgrade than the fronts. Just bigger rotors and the larger carriers & calipers to move the caliper further away from the centre. The only issue is the dust shields. To replace them with the bigger ones, you have to remove the stub axle, which usually requires new rear bearings. Or, you can 'modify' the dust shields by cutting off the lip, or bending it flat. Cut slits in the lip every couple centimeters and the tabs will bend so you can flatten the shield.

@Phatdub
i would like to have multi piston calipers on the rears and found this guy in Germany who builds a kit w rotors and adapters. his kit is advertised for MK4 VR6s.
wanted to make sure if VR6 rears are compatible w ours..

Berk, multi piston calipers are nice but the VW e-brake used a screw style piston and this is where the multi piston calipers can't connect to the e-brake system. You can get bigger discs but you will need to move the stock caliper out on some sort of bracket which looks like what this kit is all about.

With my HPA system, the e-brake is inside the rotor freeing up the caliper to have as many pistons as HPA wanted to put into it. Mine rears have 4 per caliper but I really wanted 6

We got these to stop while pulling the trailer. They are way too much for daily driving under 200 kph!

When we did the upgrade we found that the little TDI rear hubs needed some extra machining and reworking to make the tiny hubs get to the VR6 sizing. There is a good chance that the kit wont be a direct bolt on upgrade for our cars.

You do realize that as long as you can lock up the brakes/ABS kicks in, is all that you need to stop the car and the trailer. Bigger brakes do nothing for stopping. They give a "better feel" but doesn't increase the capacity unless you are on a rece track. The vehicle's weight controls the trailer when the trailer brakes fail, not the oversized brakes. The trailer will push a light car regardless how big the brakes are. Also you can easily out brake the car with a system that's too big for the car and cause drivebility problems. Bigger is not always better. 6 piston calipers on a street Beetle/Golf/Jetta is just nonsense but they do look cool especially if you laint them red or yellow.

I am sure that the car could stop the trailer and itself with the stock brakes. We were going for more responsive braking. The challenges we faced were: 1) no declared towing capacity on the car as nothing was published by VW. 2) we have a lot of crappy drivers and hills in this part of the country.

We wanted to be able to stop if quickly while still in control of the car and trailer. The bigger brakes are designed to work when the heat gets up really high.

There is a long 12 percent grade on highway 5 that we will be taking route next month. I certainly wouldn't even consider trying that with the stock brakes.

That's nice but you still not going to stop the 2000lb trailer on a 12% decline if the trailer brakes fail. The car is too light and the trailer will push it regardless how big the brakes are. There is just not enough ballast in the car for the tires to stick.